A gas turbine engine includes a compressor section, a combustion section, and a turbine section. Disposed within the turbine section and combustion section are alternating rows of rotatable blades and static vanes. These stationary vanes, disposed between rows of rotating blades, stabilize and direct the gas flow from one row of rotating blades to the next row. Such gas flow stabilization optimizes the flow of gas, thereby maximizing the amount of work extracted.
The blades are normally distributed about the periphery of the plurality of rotors or disks, turning a shaft which drives the compressor and other auxiliary systems. The most common rotor design used today in high temperature, high speed applications, such as in gas turbine engines for jet aircraft, comprises a hub with blades or airfoils mechanically attached to the hub rim, such as by the use of the well known dovetail and fir-tree shaped roots. The alloy used for the hub, or disk is selected to meet the requirements of high tensile strength and good low cycle fatigue resistance. Such properties are found, for example, in fine grain equiaxed superalloy materials. Turbine or compressor disks typically have raised portions, or protrusions, circumferentially around the face thereof in contact with knife-edge airseals, so as to prevent air flow from the rim of the disk to the center thereof, to maintain compressor and/or turbine efficiency. These protrusions are referred to as airseal lands. In general, two airseal lands are utilized, which are referred to as the inner and outer airseal lands.
Knife-edge airseals, which contact the airseal lands, are typically made from Inconel 901, and have a machined double-acting static seal lip. This seal lip rides against the vertical circumference of the airseal land of the disk. In service, abrasion and wear occur, resulting in wear grooves on the disk or compressor airseal land. When this wear exceeds a predetermined value, typically 0.012 inch in depth, the engine may lose efficiency and performance, due to air leakage. In addition, airseal lands may undergo distortion, stretching, and elongation during operation, since typical engine operating temperatures in the 600.degree.-1200.degree. F. range exist at the airseal land location of the disk. Consequently, it is an objective of the present invention to provide a method for repair of the inner and outer airseal lands.
In the compressor and turbine sections of gas turbine engines, wrought superalloys of nickel, and titanium alloys are used. Joining processes available for such alloys are limited due to the requirement to maintain mechanical properties in the repaired condition at elevated temperatures. Inertia welding is not a suitable repair technique for such situations, since the repair must be performed on finish machined hardware, and an inertia weld repair would result in significant concentricity and distortion problems due to high load requirements. It is an objective of this invention to provide a solid state joining process, such as forge-joining, where joining is performed at a temperature within the solution temperature range of the alloy of the disk, but below the incipient or bulk metal melting temperature, to provide a solid state bonding of the replacement airseal land.